Emmanuelnlopez
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Is a LiFePo4 charger just a CCCV charger?
- Thread starter Emmanuelnlopez
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sunshine_eggo
Happy Breffast!
Pretty much.
LFP are almost drop-in lead acid battery replacements.
A charger that has:
14.2-14.6 (14.2-14.4 preferred) absorption voltage
13.4-13.6V (13.5V preferred) float - float is only necessary if in a cyclic application.
Temperature compensation disabled.
Will work fine.
LFP are almost drop-in lead acid battery replacements.
A charger that has:
14.2-14.6 (14.2-14.4 preferred) absorption voltage
13.4-13.6V (13.5V preferred) float - float is only necessary if in a cyclic application.
Temperature compensation disabled.
Will work fine.
Almost. The issue you will run into is absorption time. With a CCCV charger, once the battery reaches 14.4V the charger will stay at 14.4V, and will overcharge the battery. It is important the charging stop, either by turning off, or by reducing voltage to less then 13.6V, which if the battery is at 13.8V (fully charged voltage after charging is stopped and battery resting) stops charging. If you have some other way to stop charging to use in addition to a CCCV supply, they could work. Not sure I would use the specific modules you link to, but they might work.
The voltages are compatible with lead acid. But the specifics of changing charging stages are different.
The voltages are compatible with lead acid. But the specifics of changing charging stages are different.
pollenface
Solar Addict
Personally for my complex charging needs i use a bench power supply and a timer switch.
Eg. 14.2v for 1hr
Eg. 14.2v for 1hr
Emmanuelnlopez
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Could I just set the voltage to 13.6 and never fully charge the batteries? Would this be better/worse for the batteries?
sunshine_eggo
Happy Breffast!
13.6V (3.4V/cell) is a level at which low current overcharge can occur. For a system that cycles daily, that's not a concern. If you're going to apply a float for long duration, it should not exceed 13.5V.
MisterSandals
Participation Medalist
What is your use case for this battery? Is it for standby backup power or is it used continually/frequently or ??
Emmanuelnlopez
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I'm probably going to use it continually a little bit all the time, constantly charging it, and occasionally using a lot of energy.
My plan is to charge two of them in parallel at 10A x2 with two DCDC chargers on the car's two cigar ports.
My plan is to charge two of them in parallel at 10A x2 with two DCDC chargers on the car's two cigar ports.
Sverige
A Brit in Sweden
Why would low current over charge not be a concern if your system cycles daily? You could still be trickle charging at 3.4v as the sun sets on a daily basis and each time this happens there’s surely a capacity loss as free lithium is depleted? I don’t follow the logic of why it’s not an issue if the battery is subsequently discharged, but very happy to be shown the light on this as low current overcharge is something I’ve only recently become aware of.
ps. Is there a good resource to read up all the ins and outs of LVO, as I’m interested in putting in place protections against it in my own system
sunshine_eggo
Happy Breffast!
Daily cycling implies loads during the charging period. When in float, chargers usually lag the load a bit, i.e, there is some initial loss of charge during loading that is not replenished.
It also helps to know what some builders do...
When in communication with chargers, batteries like Pylontech, SOK, EG4, etc., don't even have a float voltage. They have a "charged" voltage that is maintained if charge current is available. These voltages are > 3.45V/cell.
These are builders claiming many thousands of cycles, so either LVO isn't a concern for them, or the condition doesn't impact warranty.
Sverige
A Brit in Sweden
Wow... so constant 3.45V per cell for hours a day with potentially zero charge current..? This must equate to a higher SOC than 3.65V at 0.05C charging, surely!Daily cycling implies loads during the charging period. When in float, chargers usually lag the load a bit, i.e, there is some initial loss of charge during loading that is not replenished.
It also helps to know what some builders do...
When in communication with chargers, batteries like Pylontech, SOK, EG4, etc., don't even have a float voltage. They have a "charged" voltage that is maintained if charge current is available. These voltages are > 3.45V/cell.
These are builders claiming many thousands of cycles, so either LVO isn't a concern for them, or the condition doesn't impact warranty.
I’m interested in LCO because I realise my Electrodacus based system with only voltage based thresholds for “over voltage“ (stop charging) and “over voltage recovery” (reconnect charging) leaves me vulnerable to low current overcharge, since that over voltage threshold can get hit at any current from 100A in mid afternoon down to under an amp as the sun sets. I currently have it set to 3.52V and if I drop it much lower I’m concerned about memory cycles and capacity loss due to memory effect.
sunshine_eggo
Happy Breffast!
Not necessarily. The loads cause an initial draw, and the charger lags the loads. For illustrative purposes, if 100% SoC was achieved at 3.65/0.05C, the slight drawdown and lagging charger would see the SoC settle at 99.99%.
Memory effect is negligible and it only entails a very slight shift in the already weak voltage to SoC relationship. It is not a meaningful concern.
Does the Electrodacus just cut charge at target voltage? What triggers charge to restart?
Sverige
A Brit in Sweden
Yes it cuts the charge when the chosen ”over voltage” setpoint voltage is reached (3.52V currently), then it restarts charging when the lower recovery voltage point is reached as battery voltage declines in the absence of charging. So in practice on a normal sunny day when the battery is fully charged by early afternoon it will yo-yo between those two points. The kicker is this upper voltage can be hit the first time at full charging current which is my system is nearly 100A, then subsequently at declining current levels as the sun moves to more oblique angles, until you finally might hit the upper voltage limit for the last time at a really low charging current of 1-2A. Of course in these circumstances, each time this voltage limit is reached it’s occurring at a higher and higher SOC.
It sounds like I should back off my upper limit to 3.45V and probably lower the “over voltage recovery” setting at the same time, that’s currently around 3.37V I think. Cell balancing might become harder as that normally only happens as the cells diverge in voltage as they approach 3.5V.
sunshine_eggo
Happy Breffast!
3.45 is kinda a sweet spot for absorption, and that's where my head to go by default. 3.37 sounds like a good recovery number. Expect it to cut off much sooner and cycle more frequently. If you can still hit high SoC, I'd call it good.
Can balancing threshold be lowered to 3.40?
Can balancing threshold be lowered to 3.40?
Sverige
A Brit in Sweden
I would have thought so. I’ll have a look tomorrow and try ?
Ampster
Renewable Energy Hobbyist
It may have already been said but almost every charger and/or power supply are simple Constant Current / Constant Voltage devices. Lead Acid came up with fancy names such as Boost, Absorb, Float, Equalize and others. The reality is with most powered chargers they are limited in the current they can provide and that is the Constant Current stage. When the Constant Voltage setting is reached the internal electronics cut back the current to keep the voltage from rising and the current tapers until it hits zero or some time setting or minimum current setting, then turns off.
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I would check to make sure that your vehicle can handle 10a x2. Mine has 2 ports, but both are on the same 15a circuit.
Also, those "cigarette lighter" ports are usually technically rated for 15a, but I wouldn't draw even 10a for a long period through them. It would be pretty easy to add an additional, hard wired to battery port that can handle 20a+.
cs1234
Solar Wizard
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I would think it would be easier to run wire in an older vehicle, plus, I would definitely not want to run much continuous current through that old system, without, at least, a good inspection of all connections and wiring.Easier in some cars than others.
I say this as someone who has melted stock cigarette lighter wiring with less than 10a continuous on a hot day. I'm just glad I caught it before a fire.
If you are installing something new, for goodness sake don't use a cigarette lighter socket. I would be more inclined to use the old wiring (which is a terrible idea) but replace the lighter socket with something else. The only reliable and safe thing is to not use either the old wiring or a lighter socket.
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